The extracellular matrix plays a vital role in the normal function of complex organisms. It is implicated in organogenesis, cell differentiation, metastasis, neuronal guidance, wound healing and protective functions. A specialized sheet-like structure of the extracellular matrix, the basal lamina, underlies various tissues and is in intimate contact with the plasma membrane of the overlying cells. The major components of this structure are laminin, type IV collagen, heparan sulfate proteoglycan and entactin. The molecular structures of these molecules have been largely determined by recombinant DNA approaches and the biological activity of each molecule is being elucidated. The organization of the basement membrane varies with different tissues and undergoes dynamic changes during embryogenesis, wound healing, angiogenesis and in pathological states such as in infection, inflammation, and metastasis. Very little is known about how the basement membrane is synthesized and assembled in living organisms in the above situations. The purpose of this proposal is to examine the factors which regulate and otherwise influence the assembly of laminin and entactin into the extracellular matrix of cells and animals. The biosynthetic pathways for the extracellular matrix molecules will be manipulated with the aid of several cell lines that were selected for their distinctive characteristics. These lines will yield information on both the intracellular and extracellular fates of laminin and entactin as well as their interactions with other extracellular matrix components. As an animal model we propose to use the zebrafish, Brachydanio rerio . This small vertebrate organism has unique advantages over other vertebrates because of its size, ex corpora embryonic development, cost, and ease of genetic and biochemical manipulation. A combination of immunological, biochemical and genetic approaches will be used in these studies. It is hoped that the results obtained will contribute to our understanding of basal lamina function at the molecular level in normal development and in pathological conditions.